The present invention relates to quick-drying two-component polyurethane coating compositions, to processes for preparing them, and to their use.
Two-component polyurethane coating compositions are widespread, for example, for coating in the automobile industry. Coating systems of this kind are subject to exacting requirements in respect of qualities including scratch resistance, flexibility, and hardness.
For processing when coating, quick drying is essential, since it allows the coated substrates to be processed further more quickly.
Two-component polyurethane coating compositions comprising as their binder a combination of polyacrylateols and hyperbranched polyesters are known from WO 2005/118677, WO 03/70843, WO 06/52982, WO 07/125,029 and WO 07/125,041.
The specifications contain no reference to accelerated drying in the presence of hyper-branched polyesters.
WO 06/76715 discloses a binder mixture comprising hyperbranched polyester and polyacrylateol. Cellulose acetate butyrate is used as a crosslinker.
WO 04/94515 describes two-component polyurethane coating compositions comprising polyisocyanate/polyacrylateol/polyester for paints. No reference, however, is given to the advantage afforded by the hyperbranched polyesters.
It was an object of the present invention to provide two-component polyurethane coating compositions which exhibit improved drying relative to other two-component coating compositions.